feat: Improve file display, timezone handling, and LOT management

Changes:
- Fix datetime serialization with UTC 'Z' suffix for correct timezone display
- Add PDF upload support with extension fallback for MIME detection
- Fix LOT add/remove by creating new list for SQLAlchemy JSON change detection
- Add file message components (FileMessage, ImageLightbox, UploadPreview)
- Add multi-file upload support with progress tracking
- Link uploaded files to chat messages via message_id
- Include file attachments in AI report generation
- Update specs for file-storage, realtime-messaging, and ai-report-generation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/migrate_orphan_files.py

@@ -0,0 +1,134 @@
+"""Migration script to create messages for existing files without message_id
+
+This script:
+1. Finds all files in tr_room_files that have no message_id
+2. Creates an associated message (image_ref or file_ref) for each
+3. Updates the file record with the new message_id
+
+Run from project root:
+    python scripts/migrate_orphan_files.py
+"""
+import sys
+import os
+
+# Add project root to path
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from datetime import datetime
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import get_settings
+from app.modules.file_storage.models import RoomFile
+from app.modules.realtime.models import Message, MessageType
+from app.modules.file_storage.services.minio_service import generate_presigned_url
+
+settings = get_settings()
+
+
+def get_db_session():
+    """Create database session"""
+    engine = create_engine(settings.DATABASE_URL)
+    Session = sessionmaker(bind=engine)
+    return Session()
+
+
+def migrate_orphan_files():
+    """Migrate orphan files by creating associated messages"""
+    db = get_db_session()
+
+    try:
+        # Find files without message_id
+        orphan_files = db.query(RoomFile).filter(
+            RoomFile.message_id.is_(None),
+            RoomFile.deleted_at.is_(None)
+        ).all()
+
+        if not orphan_files:
+            print("No orphan files found. Nothing to migrate.")
+            return
+
+        print(f"Found {len(orphan_files)} orphan files to migrate.")
+
+        migrated = 0
+        failed = 0
+
+        for file in orphan_files:
+            try:
+                # Generate presigned URL for file
+                download_url = generate_presigned_url(
+                    bucket=file.minio_bucket,
+                    object_path=file.minio_object_path,
+                    expiry_seconds=3600
+                )
+
+                # Determine message type
+                if file.file_type == "image":
+                    msg_type = MessageType.IMAGE_REF
+                    content = f"[Image] {file.filename}"
+                else:
+                    msg_type = MessageType.FILE_REF
+                    content = f"[File] {file.filename}"
+
+                # Get next sequence number for the room
+                max_seq = db.query(Message.sequence_number).filter(
+                    Message.room_id == file.room_id
+                ).order_by(Message.sequence_number.desc()).first()
+                next_seq = (max_seq[0] + 1) if max_seq else 1
+
+                # Create metadata
+                metadata = {
+                    "file_id": file.file_id,
+                    "file_url": download_url,
+                    "filename": file.filename,
+                    "file_type": file.file_type,
+                    "mime_type": file.mime_type,
+                    "file_size": file.file_size,
+                }
+
+                # Add thumbnail_url for images
+                if file.file_type == "image":
+                    metadata["thumbnail_url"] = download_url
+
+                # Create message
+                message = Message(
+                    room_id=file.room_id,
+                    sender_id=file.uploader_id,
+                    content=content,
+                    message_type=msg_type,
+                    message_metadata=metadata,
+                    created_at=file.uploaded_at,  # Use original upload time
+                    sequence_number=next_seq,
+                )
+
+                db.add(message)
+                db.flush()  # Get the message_id
+
+                # Update file with message_id
+                file.message_id = message.message_id
+
+                migrated += 1
+                print(f"  Migrated: {file.filename} -> message {message.message_id}")
+
+            except Exception as e:
+                failed += 1
+                print(f"  Failed: {file.filename} - {e}")
+
+        # Commit all changes
+        db.commit()
+        print(f"\nMigration complete: {migrated} migrated, {failed} failed")
+
+    except Exception as e:
+        db.rollback()
+        print(f"Migration failed: {e}")
+        raise
+    finally:
+        db.close()
+
+
+if __name__ == "__main__":
+    print("Starting orphan files migration...")
+    print("=" * 50)
+    migrate_orphan_files()
+    print("=" * 50)
+    print("Done.")